Double voice coil loudspeaker

ABSTRACT

The present invention relates to sound reproducers or loudspeakers of the electro-dynamic or moving-coil type and to a new series-parallel circuit provided with resistance to increase the cycle range and improve the timbre of the sound.

v United States Patent 1 [111 3,766,334

Burke Oct. 16,1973

[54] DOUBLE VOICE COIL LOUDSPEA KER 2,897,291 7/1959 Burl e 179/118.5 R [76] n entor: Ambrose D. Burke North Scituate 2,922,849 1/1960 Uchida 179/115.5 DV

R.1. Primary Examiner-William C. Cooper [22] Ffled: 1971 Assistant Examiner-Thomas L. Kundert App]. No.: 198,873

Att0rney-William Frederick Werner [5 7'] ABSTRACT The present invention relates to sound reproducers or loud-speakers of the electro-dynamic or moving-coil type and to a new series-parallel circuit provided with resistance to increase the cycle range and improve the timbre of the sound.

3 Claims, 4 Drawing Figures PATENTEDUBI 16 ms. 3,766; 334

FIG./.

INVENTOR AMBROSE D. BURKE BY 9%W ATTORNEY DOUBLE VOICE COIL LOUDSPEAKER This invention relates to sound reproducers and more particularly, to loudspeakers of the electro-dynamic or moving-coil type and more specifically to improving the cycle range and sound qualities.

A primary object of the present invention is the provision in the circuit structure of a loudspeaker of resistance which will supply more harmonics or overtones than heretofore, increase the cycle range and improve the timbre of the sound, thereby providing sound which, in effect, appears to be more three dimensional in scope and less flat than sound reproduced by conventional speakers heretofore utilized.

Another object of the present invention is the provision of a loudspeaker capable of utilizing a greater output from a transformer while at the same time producing sharp and distinct tones.

Still another object of the present invention is the provision of a speaker which has virtually no resonant frequency such as usually caused by cone vibration,

and which smooths out and reduces the gain or such caused by an audio frequency.

A further object is the provision of a speaker which is exceedingly effective at low frequencies, down to 30 cycles, and to frequencies as high as 1,500 cycles.

Another object of the present invention is the provision of a loudspeaker which, although simple in construction, is nevertheless highly efficient and sensitive in operation.

Other objects of the present invention will be pointed out in part and become apparent in part in the following specification and claims.

Referring to the drawings in which similar characters of reference indicate corresponding parts:

FIG. lis a front elevation of a loudspeaker embodying the instant invention;

FIG. 2 is a rear elevation thereof, partly broken away;

FIG. 3- is an enlarged section taken on line 33 of FIG. 2; and

FIG. 4 is a detail section, partly broken away, of the outer armature utilized in the present invention.

The conventional electrodynamic loudspeaker or sound reproducer as heretofore utilized, has worked on the principle of a moving voice coil, which, when excited, usually by magnetic means, imparts vibration to the speaker cone thereby producing sound. More specifically, the moving voice coil is usually wound on a cardboard bobbin or the like which in turn is secured to the speaker cone. A magnetic field is provided proximate to said voice coil and the electrodynamic action which results between the flux produced by current passing through the wires of said coil and the magnetic lines of force creates a mechanical upward and downward pulling action. This force causes the voice coil to move up and down, which in turn makes the speaker cone vibrate and produce sound. The volume from the speaker is determined by the strength of the magnetic field, the number of turns in the voice coil, and the amount of current passing there through.

It has been found that the above-described speaker operation can be greatly improved by the use of double Referring to the drawings, a loudspeaker constructed in accordance with the instant invention is shown gen tional construction. The truncated end 20 of cone 18' has secured thereto by any desirable means, such as cementing, an outer voice coil bobbin 22 comprising a cardboard or aluminum cylinder 24 having windings 26 therearound. A cork or composition ring 28 is secured to the inner surface of the cylinder 24 and acts as both spacing and insulating means between outer coil bobbin 22 and an inner voice coil bobbin 30, likewise comprising a cardboard or aluminum cylinder having windings therearound. It will be understood that the inner voice coil bobbin 30 is secured to the spacer 28 and is maintained solely thereby in concentric relation with respect to outer voice coil bobbin 22. It will further be understood that the bobbins 22 and 30, other than the formers connection to speaker cone 18, are not anchored in any way and hence are free to move axially whereby to impart vibration to the speaker cone 18.

Secured to the truncated end of shell 12 by any desirable means, as at 32, is a metallic rectangular supporting strap 34. Supporting strap 34 comprises a rear wall 36, side walls 38 and a front wall 40 having therein a centrally disposed aperture 42, the inner surface 43 of which comprises a pole face. Mounted on the inner surface of rear wall 36, as by cementing or the like, is a permanent magnet 44, although it will be understood that other forms and types of magnets, such as an electromagnet, for example, could well be utilized. Magnet 44 at its free end forward surface engages inner and outer poles 46 and 48, respectively, now to be described. It will be understood that poles 46 and 48 are each contructed of magnetic steel and hence, due to their contact with magnet 44, provide their respective magnetic fields. The outer pole 48 comprises a tubular body portion 50, the outer diameter of which extends through the aperture 42 in spaced relation to pole face 43 thereof, whereby to provide a gap 51. Pole 48 further comprises an outwardly extending peripheral flange 52 which is in contact with magnet 44. Inner pole 46 comprises a core portion 54, and likewise is provided with an outwardly extended flange 56. As will be noted, inner pole 46 is mounted concentrically within outer pole 48 by virtue of the fact that flange 56 is a press-fit therein. A circular spacer ring 57 of nonmagnetic material, such as brass, maintains outer pole 48 against longitudinal movement, and also maintains poles 46 and 48 centered with respect to the aperture 42.

In operation and use, outer voice coil bobbin'22 surrounds outer pole 48 in very close proximity thereto and extends into gap 51, while inner voice coil bobbin 30 is disposed intermediate core 54 of the inner pole and tubular portion 50 of the outer pole. As will be noted clearly in FIG. 3, tubular portion 50 does not extend inwardly of gap 51, thereby leaving uncovered a substantial portion of the windings of bobbin 30. As will hereinafter become apparent, this relation is important in that it enables vibrations from one bobbin to be imparted to the other, whereas if such tubular portion extended in appreciably farther, it would tend to isolate the two bobbins with respect to each other.

It has been found that'much improved sound characteristics are achieved in my specific structural arrangement by providing a non-magnetic coating 58 on the inner surface of tubular portion 50. It will be understood that this coating may be of any material which is incapable of being magnetized or attracted by a magnet, some examples of such material being so-called white metal, brass, aluminum, copper, etc.

Another important feature of the instant invention resides in the fact that the space 59 between voice coil bobbins 22 and 30 acts, in effect, as a soundcompression chamber. In other words, the sound vibration waves which emanate from the outer bobbin 22 will be carried across the chamber 59 and imparted to the inner bobbin 30 and vice versa. Hence, in effect, each voice coil bobbin cooperates with the other to produce more pronounced vibration of the speaker cone. In this respect it might be pointed out that the windings on either bobbin 22 or 30 could be eliminated, and the loudspeaker would still function in improved fashion. More specifically, if, for example, the windings 26 of outer bobbin 22 were eliminated, the vibrations emanating from inner bobbin 30 would still move across chamber 59 and be imparted to the cylinder 24, thereby causing the latter to aid in vibrating the speaker cone.

Conventional terminals 60 and 62 and wiring 64 and 66 are provided for the energization of the voice coils. Also, a conventional spider 68 may be utilized, if desired, to help maintain the voice coils in proper position and also to act as a dust shield.

FIG. 2 is a wiring diagram showing outer voice coil bobbin terminal 22 and inner voice coil bobbin terminal 30. A first electrical conduit 66 (which may be considered to be negative or ground) is connected on one end to outer voice coil bobbin terminal 22 and on the other end it may be connected to an amplifier (not shown). A second electrical conduit 64 (which maybe considered to be positive) is connected on one end to outer voice coil bobbin terminal 22 and on the other end to the amplifier (not shown). A first auxiliary electrical conduit 66A connects inner voice coil bobbin terminal 30 with second electrical conduit 64. A second auxiliary electrical conduit 64A connects inner voice coil bobbin terminal 30 with second electrical conduit 64. An electrical resistance, which may take any known form, is illustrated as a resistor 75 intermediate the connections of conduits 64A and 66A with conduit 64. In this manner by way of example an 8 ampere current from the amplifier will flow through electrical conduit 66 and outer coil 22 to the parallel circuit of resistor 75 and inner coil 30. 4 amperes will flow through resistor 75 and 4 amperes will flow through coil 30 (assuming equal resistances), whereby reactants are created which are fed back to electrical conduit 64. This feedback assists the frequencies to thereby increase the cycle range to thirty cycles on the low end of the scale to 15,000 cycles on the high end of the scale. The timbre of the music is thereby greatly enhanced.

Having shown and described a preferred embodiment of the present invention by way of example, it should be realized that structural changes could be made and other examples given without departing from either the spirit or scope of this invention.

What I claim is:

1. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustroconical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, an outer voice coil bobbin, an inner voice coil bobbin, mounted concentrically with respect to each other, means securing one of said voice coil bobbins to said speaker cone in axially extending relation therefrom, means comprising an insulating and spacing collar attached to said compression chamber, and pole faces disposed adjacent the outer surface of the outer voice coil bobbin and cooperating with said second pole to form a gap, said second pole tubular portion having on the inner surface a non-magnetic metallic coating to isolate the magnetic field of said second pole from the magnetic field of said first pole, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and tosaid second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical coduits and voice coils being arranged in inphase relation.

2. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustroconical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, inner and outer voice coil bobbins mounted concentrically with respect to each other, means securing said outer voice coil bobbin to speaker cone in axially extended relation therefrom, a spacing collar of magnetic insulating material secured to both said inner and outer voice coil bobbins to rigidly support said bobbins in concentric relationship and to define an annular sound compression chamber therebetween, means for creating a magnetic field in juxtaposition to each of said bobbins, said magnetic means comprising a permanent magnet, a first pole attached to said permanent magnet and provided with a core portion extending within the inner voice coil bobbin, a second pole attached to said permanent magnet and mounted concentrically with respect tosaid first pole and provided with a tubular portion extending into said sound compression chamber, a gap formed between said first and second poles, said second pole tubular portion having on the inner surface a nonmagnetic metallic coating to control the effective force of the magnetic field of said first pole, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical conduits and voice coils being arranged conduits in-phase relation.

3. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustroconical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, inner and outer voice coil bobbins mounted concentrically with respect to each other, means securing said outer voice coil bobbin to said speaker cone in axially, extending relation therefrom, a spacing collar of magnetic insulating material secured to both said inner and outer voice coil bobbins to rigidly support said bobbins in concentric relationship and to define an annular sound compression chamber therebetween, means for creating a magnetic field consisting of a circular strap having an axial orifice and open opposite sides, a block formed in the circular strap opposite the axial orifice, said circular strap and block comprising a low loss permanent magnetic circuit, a first pole bar magnet attached to said block and provided with a core portion extending within the inner voice coil bobbin, a second pole attached to said block, mounted concentrically with respect to said first pole and provided with a tubular portion extending into said sound compression chamber end of said sound compression chamber, said inner and outer voice coil bobbins and said first and second pole's extending axially through said axial orifice to form a first gap between said circular strap at said axial orifice and said outer voice coil bobbin, and a second gap formed between said first and second poles, said second pole tubular portion having on the inner surface'a non-magnetic metallic coating to control the effective magnetic field between said first pole bar magnetic and said second pole low loss magnetic circuit, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical conduits and voice coils being arranged in inphase relation. 

1. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustroconical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, an outer voice coil bobbin, an inner voice coil bobbin, mounted concentrically with respect to each other, means securing one of said voice coil bobbins to said speaker cone in axially extending relation therefrom, means comprising an insulating and spacing collar attached to said outer voice coil bobbin and attached to and supporting said inner voice coil bobbin in spaced relation and defining therebetween an annular sound compression chamber, means for creating a magnetic field in juxtaposition to each of said bobbins, said magnetic means comprising a first pole having a core portion extending within the inner voice coil bobbin, a second pole comprising a tubular portion extending into said sound compression chamber, and pole faces disposed adjacent the outer surface of the outer voice coil bobbin and cooperating with said second pole to form a gap, said second Pole tubular portion having on the inner surface a non-magnetic metallic coating to isolate the magnetic field of said second pole from the magnetic field of said first pole, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical conduits and voice coils being arranged in inphase relation.
 2. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustro-conical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, inner and outer voice coil bobbins mounted concentrically with respect to each other, means securing said outer voice coil bobbin to speaker cone in axially extended relation therefrom, a spacing collar of magnetic insulating material secured to both said inner and outer voice coil bobbins to rigidly support said bobbins in concentric relationship and to define an annular sound compression chamber therebetween, means for creating a magnetic field in juxtaposition to each of said bobbins, said magnetic means comprising a permanent magnet, a first pole attached to said permanent magnet and provided with a core portion extending within the inner voice coil bobbin, a second pole attached to said permanent magnet and mounted concentrically with respect to said first pole and provided with a tubular portion extending into said sound compression chamber, a gap formed between said first and second poles, said second pole tubular portion having on the inner surface a nonmagnetic metallic coating to control the effective force of the magnetic field of said first pole, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical conduits and voice coils being arranged in in-phase relation.
 3. A loudspeaker of the electrodynamic type, comprising dual voice coils driving a substantially frustro-conical speaker cone, whose sound output is monaural and whose sound intensity is equal and audible at each ear, said dual voice coils comprising, inner and outer voice coil bobbins mounted concentrically with respect to each other, means securing said outer voice coil bobbin to said speaker cone in axially extending relation therefrom, a spacing collar of magnetic insulating material secured to both said inner and outer voice coil bobbins to rigidly support said bobbins in concentric relationship and to define an annular sound compression chamber therebetween, means for creating a magnetic field consisting of a circular strap having an axial orifice and open opposite sides, a block formed in the circular strap opposite the axial orifice, said circular strap and block comprising a low loss permanent magnetic circuit, a first pole bar magnet attached to said block and provided with a core portion extending within the inner voice coil bobbin, a second pole attached to said block, mounted concentrically with respect to said first pole and Provided with a tubular portion extending into said sound compression chamber and forming part of said low loss magnetic circuit, the forward surface of said second pole forming the other end of said sound compression chamber, said inner and outer voice coil bobbins and said first and second poles extending axially through said axial orifice to form a first gap between said circular strap at said axial orifice and said outer voice coil bobbin, and a second gap formed between said first and second poles, said second pole tubular portion having on the inner surface a non-magnetic metallic coating to control the effective magnetic field between said first pole bar magnetic and said second pole low loss magnetic circuit, a first electrical conduit attachable to an amplifier, and to said outer voice coil bobbin, a second electrical conduit attachable to an amplifier and to said outer voice coil bobbin, a first auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, a second auxiliary electrical conduit connected to said inner voice coil bobbin and to said second electrical conduit, and resistance means interposed in said second electrical conduit intermediate said first auxiliary electrical conduit and said second auxiliary electrical conduit said electrical conduits and auxiliary electrical conduits and voice coils being arranged in in-phase relation. 